John Jeffreys Pratt, 1st Marquess Camden, KG, PC, FSA (11 February 1759 – 8 October 1840), styled Viscount Bayham from 1786 to 1794 and known as the 2nd Earl Camden from 1794 to 1812, was a British politician. He served as Lord Lieutenant of Ireland in the revolutionary years 1795 to 1798 and as Secretary of State for War and the Colonies between 1804 and 1805.